Studies of medical treatment adherence suggest that substantial percentages of persons do not comply with recommendations given to them for the treatment of acute and chronic health conditions. Insulin dependent diabetes mellitus (IDDM) is a chronic health conditions with a highly complex medical regimen. Substantial data exist that suggest that improving treatment adherence and metabolic control in persons with IDDM can delay the onset of diabetes complications. Unfortunately, those adolescents with IDDM with the poorest diabetes self-management and metabolic control are often the most resistant to hospital-based health care and traditional educational/supportive interventions. They are also faced with multiple barriers to improved adherence, including lack of knowledge about diabetes, family disorganization and conflict, high levels of stress and limited social support and access to community resources. Multisystemic Therapy (MST) is a family and community-based treatment model which has previously been used with adolescents presenting with serious mental health problems. MST has been shown to be both "effective" and highly transportable to the types of community settings where care is most often provided. Preliminary data suggest that MST is a promising approach for adolescents with IDDM as well. The objective of the present study is to utilize MST to improve the treatment adherence and metabolic control of urban adolescents with IDDM and a glycoslated hemoglobin of 11 percent or above. Additional aims are to determine the stability of MST's effects on treatment adherence and metabolic control over a two year interval, to test hypotheses about mediators of MST treatment effects and to assess the cost-effectiveness of MST when compared to the costs of short-term diabetes complications such as diabetic ketoacidosis (DKA). The experimental design for the present study is a randomized controlled trial with a sample of 100 adolescents, 50 of whom will receive MST in addition to their standard care and 50 of whom will receive only standard care of their IDDM. If successful, MST will provide immediate assistance to a vulnerable population at high risk for diabetes complications and quality of life and may also result in substantial health care savings.